Calculate the percentage change and estimated doubling or halving time between two quantitative beta-hCG blood results.
Enter two lab results
Use the same laboratory unit for both values.
Your calculation
Estimated doubling time
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How the hCG calculation works
For a rising value, doubling time is calculated from the ratio of the second result to the first and the exact elapsed time. For a falling value, the same exponential formula reports an estimated halving time. Equal values are reported as no measurable change rather than an infinite doubling time.
Why a number cannot diagnose a pregnancy
hCG patterns vary with gestational timing and individual circumstances. A single result, a doubling-time calculation, or a comparison with an online range cannot confirm a healthy pregnancy or diagnose miscarriage, ectopic pregnancy, or molar pregnancy. Clinicians interpret symptoms, serial laboratory results, ultrasound, and medical history together.
Frequently asked questions
What is quantitative hCG?
A quantitative blood test measures a specific concentration of human chorionic gonadotropin rather than giving only a positive or negative result.
Does hCG always double every 48 hours?
No. The rate varies, changes as pregnancy progresses, and cannot be judged safely from a universal rule.
What if the two results are from different laboratories?
Methods and reference ranges may differ. Ask the treating professional whether the results can be compared directly.
When should I seek urgent care?
Seek urgent medical help for severe or one-sided abdominal pain, shoulder pain, fainting, heavy bleeding, breathing difficulty, or other concerning symptoms.
Medical notice
This calculator performs mathematics only. Do not use it to diagnose pregnancy viability or decide whether to start, stop, or delay medical care. Discuss serial hCG results with the clinician who ordered the tests.
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